There exists in the United States a large quantity of coal which cannot be economically used as a fuel because of its high sulfur content. Environmental laws are such that it is economically unfeasible to burn a high sulfur content coal because of the expensive antipollution equipment required.
High sulfur coal, i.e., about 3%, exists in unmined form and also in the form of already mined coal that has been discarded, i.e., refuse coal. Refuse coal usually consists of fines which result from the processing of coal. More particularly, when coal is mined it is normally crushed and washed and the washings are generally dumped and used as land fill or dumped into a lake or stream. In the latter case, over a period of time, the pond or stream becomes almost completely filled with the finely powdered coal. Not only is this a significant waste of coal but it is injurious to the lakes and streams. Many lakes have become "dead" lakes due to this disposal of waste coal. The ash content of such refuse coal, i.e., above 20% by weight, also makes it economically unattractive to attempt to utilize it.
There also exist in the United States substantial deposits of unmined or virgin coal having a high sulfur content. In order to burn such coal in industry it would be necessary to spend substantial amounts of money for air pollution equipment. Therefore, this high sulfur content coal is not being mined.
The need to effectively utilize energy while at the same time protecting our environment faces many other industries as well, the steel industry being another example. The disposal of waste materials from steel making processes in an economically feasible, environmentally suitable manner is frequently a significant problem. For example, in the processing of steel an acid solution (pickle liquor) is used to treat the product. The resultant solution consisting of acid, iron compounds, contaminants, etc. (collectively referred to hereinafter as spent pickle liquor) must be disposed of.